Pain & Neuroscience, Discovery Research Laboratories for Core Therapeutic Areas, Shionogi & Co., Ltd., 1-1 Futaba-cho, 3-chome, Toyonaka, Osaka 561-0825, Japan.
Antibody Therapeutics, Discovery Research Laboratory for Innovative Frontier Medicines, Shionogi & Co., Ltd., 1-1 Futaba-cho, 3-chome, Toyonaka, Osaka 561-0825, Japan.
Osteoarthritis Cartilage. 2016 Jul;24(7):1254-62. doi: 10.1016/j.joca.2016.02.010. Epub 2016 Mar 9.
To assess the functional changes of Transient receptor potential vanilloid 1 (TRPV1) receptor and to clarify its mechanism in a rat mono-iodoacetate (MIA)-induced joint pain model (MIA rats), which has joint degeneration with cartilage loss similar to osteoarthritis.
Sensitization of TRPV1 in MIA rats was assessed by transient spontaneous pain behavior induced by capsaicin injection in knee joints and electrophysiological changes of dorsal root ganglion (DRG) neurons innervating knee joints in response to capsaicin. Mechanisms of TRPV1 sensitization were analyzed by a newly developed sandwich enzyme-linked immunosorbent assay that detects phosphorylated TRPV1, followed by functional and expression analyses of protein kinase C (PKC) in vivo and in vitro, which involves TRPV1 phosphorylation.
Pain-related behavior induced by intra-articular injection of capsaicin was significantly increased in MIA rats compared with sham rats. In addition, capsaicin sensitivity, evaluated by capsaicin-induced inward currents, was significantly increased in DRG neurons of MIA rats. Protein levels of TRPV1 remained unchanged, but phosphorylated TRPV1 at Ser800 increased in DRG neurons of MIA rats. Phosphorylated-PKCɛ (p-PKCɛ) increased and co-localized with TRPV1 in DRG neurons of MIA rats. Capsaicin-induced pain-related behavior in MIA rats was inhibited by intra-articular pretreatment of the PKC inhibitor bisindolylmaleimide I. In addition, intra-articular injection of the PKC activator phorbol 12-myristate 13-acetate increased capsaicin-induced pain-related behavior in normal rats.
TRPV1 was sensitized at the knee joint and at DRG neurons of MIA rats through PKC activation. Thus, TRPV1 sensitization might be involved in chronic pain caused by osteoarthritis.
评估瞬时受体电位香草酸 1 型（TRPV1）受体的功能变化，并阐明其在大鼠单碘乙酸（MIA）诱导的关节痛模型（MIA 大鼠）中的机制，该模型具有类似骨关节炎的关节退化和软骨丧失。
通过向膝关节注射辣椒素诱导瞬发性自发疼痛行为和对辣椒素反应的膝关节背根神经节（DRG）神经元的电生理变化来评估 MIA 大鼠 TRPV1 的敏化。通过新开发的检测磷酸化 TRPV1 的夹心酶联免疫吸附试验分析 TRPV1 敏化的机制，然后在体内和体外分析蛋白激酶 C（PKC）的功能和表达分析，涉及 TRPV1 磷酸化。
与 sham 大鼠相比，MIA 大鼠关节内注射辣椒素引起的疼痛相关行为明显增加。此外，MIA 大鼠 DRG 神经元中辣椒素诱导的内向电流评估的辣椒素敏感性明显增加。DRG 神经元中 TRPV1 的蛋白水平保持不变，但 MIA 大鼠中 TRPV1 的 Ser800 磷酸化增加。PKCɛ 的磷酸化-PKCɛ（p-PKCɛ）增加并与 MIA 大鼠 DRG 神经元中的 TRPV1 共定位。PKC 抑制剂双吲哚马来酰亚胺 I 关节内预处理可抑制 MIA 大鼠的辣椒素诱导的疼痛相关行为。此外，关节内注射 PKC 激活剂佛波醇 12-肉豆蔻酸 13-醋酸盐可增加正常大鼠辣椒素诱导的疼痛相关行为。
通过 PKC 激活，MIA 大鼠膝关节和 DRG 神经元中的 TRPV1 被敏化。因此，TRPV1 敏化可能与骨关节炎引起的慢性疼痛有关。
